Metal structural members have a wide-ranging applicability as components in various types of structural frames. The members may be used, for example, in aircrafts and automobiles to form a structural frame. The members might also find applicability in building construction and consumer devices. Another potential application is in spacecraft. The members are typically elongated components. A critical property for structural members is strength to weight ratio. Weight is an obvious drawback in many applications, just as strength is an obvious advantage.
Conventional structural metal members are composed of rolled or extruded components with constant cross-sectional size and shape, and a constant wall thickness. Typically, the cross-section of a member is circular so that the overall shape of the support member is cylindrical. However, the member may have a rectilinear cross-section. Generally, the strength to weight ratio in these types of members is a function of the material and the wall thickness, which might be thick enough to form a substantially solid member in some instances or a substantially hollow member in other instances.
Selection or design of a particular component with a specific wall thickness and cross-sectional geometry is determined by the maximum loads and stresses a particular portion or portions of that member will be required to transfer or absorb in specified service conditions. Put another way, the cross-sectional size and wall thickness of the entire length of the structural member is dictated by the point or points of maximum stress (plus an added safety factor), and the component is oversized (i.e., contains excess material and strength) elsewhere along its straight or curvilinear length. Increased wall thickness of a hollow support member increases the strength of the member (up to an internally solid structure), but with a resultant increase in the materials needed to produce the member, and the overall weight of the member. Likewise, the cross-sectional size can be increased with a resultant increase in materials.